Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge.
Geologists spend many hours and much computing time modelling the distribution of minerals throughout a rock mass. Significant investments in exploratory drilling and assaying are also made before geostatistical techniques are applied to the collected data to interpolate the extents and distribution of the valuable metals contained in the ore. A large body of work exists in this field, such that the block model of the resource is a reasonably accurate reflection of the mineral that is actually in the ground prior to blasting. Blasting of both the mineral bearing, and waste rock, imparts energy to break the rock mass into smaller particles which allows excavation and further size reduction using methods such as crushing. Invariably some of this blasting energy is expended moving the rock mass also, displacing the known ore boundaries from where they were originally defined by the grade control engineers or geologists.
Failure to accurately account for ore movement due to blasting will result in misclassification, from ore to waste; low to high grade; sulfide to oxide; etc. Collectively this is referred to as ore loss and dilution and the financial consequences of getting this wrong can be significant.
FIG. 1 illustrates an extreme example of how ore loss and dilution might occur in a blast. In this case, the ore has moved entirely beyond the polygon it would have occupied prior to blasting. If ore movement were not taken into account, the ore (i.e. the rock that contains the commodity of interest, e.g. gold or copper) would be excavated as waste and discarded (ore loss), and waste material would be sent to the processing plant, where valuable energy and water would be expended in crushing and grinding processes for no return at all (dilution).
Traditionally, ore movement of the rock is monitored using some sort of marker (either electronic or physical). These must be placed into the rock before the blast, their location surveyed, and then found again after the blast to allow movement vectors to be calculated using the surveyed coordinates. It will be realized that it would be desirable if an alternative approach were provided which did not require the user having to measure the start and finish locations of the sensor.
Another problem that occurs in the mining industry is that of measuring the depth and angle of drill holes. It is important to be able to accurately measure the depth and angle of drill holes because this ultimately defines the distribution of explosive energy in the blasted rock mass. For example, if blast holes are too short, there will be insufficient breakage of the rock at the bottom of the blast hole. This will result in hard digging or even the inability to excavate the blast to the target level. Poor fragmentation will also have significant impact on the downstream processes such as crushing and grinding. There are other reasons too for wanting to be able to check that holes have been drilled to plan. One reason is that inaccurate drilling may reflect an inability of the site to meet fundamental metrics that define how close to best practice they are. In short, sloppy drilling will lead to sloppy blasting and then poor diggability and fragmentation.
It would also be advantageous if more information could be gathered during a blast. For example, it would be helpful if more information than merely the pre-blast and the post-blast locations of the marker might be determined.
It is an aspect of the present invention to provide a rock movement sensor that overcomes or at least alleviates a problem described above. It is another aspect to provide a useful rock movement sensor as an alternative to prior art devices.
The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.